Large earthmoving vehicles, such as tractors, loaders, off-highway trucks, and the like employ hydraulic jacks and/or suspension struts that are exposed to all varieties of dirt, debris, moisture and other abrasive contaminants. It is well known that such contaminants are injurious to the seals, bearings and other components of such jacks or struts. Accordingly, it has been the practice to use rod wipers to wipe the rod clean as it is retracted into the cylinder so as to reduce to the maximum extent possible the amount of contaminants reaching the seals and bearings. U.S. Pat. Nos. 3,866,923 issued Feb. 18, 1975 to Gerald W. Gorman and 4,618,153 issued Oct. 21, 1986 to Rolf Nilsson both disclose rod Wipers for this purpose.
In order to satisfactorily perform the desired wiping function, such wipers must remain in continuous wiping contact with the rod as it moves back and forth through the wiper. Also, the wiping contact must be applied with a sufficient radial force to ensure the desired cleaning action on the rod. These tasks are complicated in earthmoving applications by the fact that extreme side loads are exerted on the rods of hydraulic cylinders in operation, which causes the rapid radial displacement of the rod relative to the wiper as the rod moves axially in and out of the cylinder and also by the fact that earthmoving vehicles work in conditions ranging from arctic to tropic temperatures extremes. Prior wipers have been made of rubber to attain this necessary resiliency and responsiveness. However, rubber is relatively soft and susceptible to a high wear rate. Harder plastic materials, such as polyurethane for instance, exhibit much greater wear resistance. Unfortunately, two problems exists with the use of such harder materials. First, harder materials have lower creep resistance. This allows the radial force they exert on the rod to lessen over time, allowing debris to get past the wiper. Second, they have a much lower response rate, particularly at extremely low temperatures, due to their higher flex modulus and decreased resiliency at arctic temperatures. In other words, such materials do not respond quickly enough to afford their movement with the rapid radial displacements of the rod. This causes the wiper to leave contact with the rod and also allows debris to get past the wiper.
The present invention is directed to overcoming the shortcomings of the prior attempts at providing a resilient wiper with acceptable wear life.